The present invention relates to a tomography device used in medical fields and industrial fields such as nondestructive testing, RI (radio isotope) testing, and optical testing.
Examples of these types of devices include fluoroscope devices and C-arm fluoroscopic devices. These type of devices can, for example, be equipped with an X-ray detector in the form of an FPD (flat-panel detector) and an X-ray tube facing the detector. A worktop (bed) on which a detection body is mounted is raised and lowered or moved horizontally. A tomographic image of the detection body is obtained by performing a scan so that the X-ray detector and the X-ray tube are moved horizontally in opposite directions (e.g., see Japanese laid-open patent publication number 2002-267622 (page 4, FIG. 1, FIG. 2)).
The device of the above reference, however, has the following problems. When X-rays are radiated from the X-ray tube during the scanning operation, there is a cross section known as a focal plane. This focal plane provides the most effective X-ray field of view. The region for which a tomographic image can be reconstructed is broadest for this focal plane, and the region where this reconstruction can take place becomes narrower the further away one is from the focal plane. Thus, there can be cases where the detection body being observed falls outside the region within which image reconstruction is possible. Since the relationship between the bed height and the position of the focal plane is known, conventional tomographic imaging places the body within the region where reconstruction is possible by adjusting the bed-height factor of the imaging conditions. Stated another way, it is difficult to adjust imaging conditions for the reconstruction range in any way other than adjusting the bed height.